Animal Responses Flashcards
What is the CNS ?
- made up of brain + spinal cord
- areas of grey and white matters (mylein)
What is PNS?
- consists of motor + sensory neurone system
- sensory = carry action potential from receptors to CNS
- motor = action potential from CNS to effectors
what is motor neurone system divided into ?
- somatic nervous system = conscious + voluntary control , mostly myelinated neurones
- autonomic nervous system = unconscious, involuntary control , non- myelinated
what does sympathetic system do
- fight or flight
SPEEDS UP - inc heart rate, ventilation, pupil dilation,
uses NORADRENALINE
Digestion inhibited
Vasoconstriction + inc sweating
What does parasympathetic system do
SLOWS DOWN
- rest and digest
Dec heart + ventilation rate, pupils constrict
Uses ACETYLCHOLINE
Digestion activated
Mechanism of adrenaline
- adrenaline binds to the receptor on the cell surface membrane of the target cell ( complementary in shape)
- this stimulates G protein which activated adenyl cyclase (enzyme)
- converts ATP to cAMP (2nd messenger)
- cAMP causes a cascade of enzymes
what happens when blood pH is low ?
low Ph = high CO2
- chemoreceptors in CAROTID artery + brain + aorta detect change in pH
- chemoreceptors send impulses to cardiovascular/stimulatory centre in medulla oblongata
- cardiovascular centre sends impulse to via accelerator nerve = more adrrenaline + noradrenaline to be released to SAN
- SAN works to increase heart rate.
what happens when blood pH is high ?
- chemoreceptors on carotid artery detect change
- send impulses to cardioinhibitory centre in medulla oblongata
- cardioinhibitory centre sends impulse via the vagus nerve = causes more Ach to be released
- Ach binds to receptors on SAN = SAN works do decrease heat rate
what happens when blood pressure is high ?
stretch/baroreceptors in carotid sinus detect change
- sends impulse to cardivascular centre in medulla oblongata
- sends impulses via vagus nerve = releases Ach to SAN in heart
- SAN= decreases heart rate
what happens when blood pressure is too low ?
- stretch/ baroreceptors in carotid sinus detect change
- send impulses to cardiovascular centre in medulla oblongata
- cardiovascular centre sends impulse via accelerator nerve = releases noradrenaline to SAN
- SAN = increases heart rate
Structure + function of involuntary muscle (smooth)
Structure :
- controlled unconsciously (contracts automatically)
- no striations (smooth)
- uni-nucleated ( 1 nucleus)
- spindle-shaped cells
Function: peristalsis
Structure + function of voluntary muscle ( skeletal)
- controlled consciously
- multinucleated
- has striations
- contains myofibrils
- cylindrical shaped cells
function = movement of joints
Structure + function of cardiac muscle
- myogenic but controlled by autonomic NS
- uninucleated
- intercalated discs
- branching
function = to pump blood
structure of myofibrils
- thick myofilaments = made of protein myosin
- thin = protein actin
- A bands = dark contain only myosin
- I band = light - actin
- made up of short units called sarcomere
events of muscle contraction
- action potential arrives at motor neurone
- triggers voltage-gated ca2+ channels to open + influx of ca2+ ions
- ca2+ triggers vesicles containing acetylcholine to fuse with pre-synaptic membrane + release Ach by exocytosis
- Ach diffuses across synaptic cleft
- binds to receptors on sarcolemma of Na+ ion channel
- na+ channel opens = creates wave of depolarisation = moves down T tubule to sarcoplasmic reticulum .
Ach broken down into acetate and choline by actelycholine esterase to inhibit further activation + make new acetylcholine
- wave of depolarisation moves down t -tubule to sarcoplasmic reitculum = releaes ca2+ ions into sacrcoplasm
- ca2+ binds to troponin = changes position of tropomyosin = unblocks myosin binding site on actin filaments
- myosin head binds + forms cross- bridge + pulls actin filament along (releases ADP)
new ATP binds to myosin head = breaks cross-bridge + myosin detaches
ca2+ ion activates ATPase on myosin head = hydrolyses ATP into ADP and pi
energy released turns mysoin head to og position
- ca2+ ions actively transported out of sarcoplasm into sacrcoplasmic reticulum
troponin returens to og shape + pulls tropomyosin = blocks binding site again
= stops muscle contractions
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